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Transponder and ADS-B Requirements

For the airspace listed below, aircraft are required to have a Mode S or transponder (used on advanced aircraft for TCAS), or Mode C transponder with pressure altitude encoding.

And an ADS-B out source operating on:

  • 1090 MHz Extended Squitter (TSO-C166b)
  • 978 MHz Universal Access Transceiver (UAT) (TSO-C154c)
91.215(b) 91.225(a)

Transponder Operation​

If you have an operational transponder and ADS-B out solution, then it must be operated at all times in controlled airspace.

91.215(c) 91.225(f)

Required Airspace​

  • Within Class A, B and C airspace
  • Above the lateral bounds of Class B and C airspace
  • Within 30nm of a Class B airport (the Mode C Veil), up to 10,000' MSL
  • At and above 10,000' MSL over the contiguous states, excluding the airspace at and below 2,500' AGL
  • Class E airspace at and above 3000' MSL, over the Gulf of Mexico from the coastline of the United States out to 12 nautical miles
91.215(b) 91.225(d)

Exceptions​

Aircraft that were not originally certificated with an engine-driven electrical system or which has not subsequently been certified with such a system installed, balloon, or glider.

ATC Deviations​

ATC deviations from these requirement (for both Mode C transponder and ADS-B out), can be made in several scenarios:

  • If you have an operational transponder that isn't Mode C, you can request a deviation at any time
  • If you have an inoperative transponder/ADS-B out source, and you are travelling to a destination (including any intermediate stops) where repairs can be made, you can request a deviation at any time
  • If your aircraft is not equipped with a transponder or ADS-B position source, you can request a deviation at least 1 hour before your proposed operation
91.215(d) 91.225(f)